The present invention relates in general to electronic key validation and, more particularly, to encrypting data for key validation.
Vehicle security is a major concern especially in high-crime metropolitan areas. In the past, vehicle security has often been limited to mechanical keys with serrated edges that must match a lock tumbler pattern in order to unlock the door and engage the ignition to start the engine. Mechanical keys are relatively easy for professional thieves to overcome. Special tools can rotate the tumblers of the door lock, or the thief can simply break a window to gain entry. Once inside the vehicle, it is relatively easy to remove the ignition switch and electrically bypass it. Conventional keys offer relatively limited protection against the professional thief.
Mechanical locks provide a first level of security for entry and operation of the automobile. The automobile control system allows starting of the engine. As a second level of security, the key is also be electronically validated within a short time for the auto to continue operating. The automobile control system sends a predefined security request to the key by inductive coupling to validate the identification and authorization of the key. If the key does not provide the correct security response code, the automobile control system shuts down the engine, locks out all functions, and possibly sounds an anti-theft alarm.
More recent developments provide for remote keyless entry (RKE) where the owner can press a button on the key or other device some distance from the auto to lock or unlock the doors, unlatch the trunk, turn on head lights, set off a panic alarm, or any one of a number of other functions. The key or device broadcasts a security code and command by infrared or radio frequency (RF) transmission. The vehicle responds to the command only if the security code matches its internally stored code. The security codes can be set at the factory or transmitted as rolling encrypted codes, i.e. one that changes each transmission.
The RKE security system is not fool-proof. One weakness of the RKE security systems that do not use rolling encryption codes is that a sophisticated thief can monitor the broadcast and record the security ID and access codes. Alternatively, if the key is left with a repair facility, an unscrupulous person can relatively easily copy the fixed security codes by sending a security request and monitoring the response. .The dishonest person need only re-transmit the same security code to gain access at an opportune time. Prior art implementations of rolling encryption codes tend to be quite complex.
Hence, a need exists for a simple yet effective security protection scheme.